Effort reduction system for the actuation of the clutch pedal for motor vehicles

ABSTRACT

A system for reducing the force to actuate the clutch pedal in automobiles is described, wherein the clutch-actuating pedal ( 2 ) is fixed to one end of an actuating arm ( 1 ), which has, at its other end, a pivot pin ( 3 ) as an integral part of the free end of the rod ( 4 ), the actuating arm ( 1 ) being further pivoted around a pivot pin ( 6 ) located between its ends and fixed tot he vehicle body (not shown), so that a force applied on to the pedal ( 2 ) causes the pivot pin ( 3 ), provided at the other end of the actuating arm ( 1 ), to actuate, pressing the rod ( 4 ) of the plunger of the clutch master cylinder ( 5 ). This invention reduces the actuating force by means of a system in which the actuating arm ( 1 ), upon actuating the pedal ( 2 ), pivot pin ( 3 ) and, consequently, the lever arm (X), where the force on the rod is applied, describe a rotational path (A) around the pin ( 6 ). The component of the lever arm (X), which influences the moment applied to the pin ( 6 ), decreases as the lever arm follows the path (A), thus reducing the moment and the effort required from the driver to actuate the clutch. In addition, the master cylinder ( 5 ) itself is pivotable around a pin ( 9 ), fixed to the support ( 10 ) on the vehicle body, allowing the rod ( 4 ) to accommodate the pivot pin ( 3 ), when the latter follows the path (A), so as to enable the rod ( 4 ) to penetrate further into the master cylinder ( 5 ) of the clutch.

[0001] The invention refers to a system designed to reduce the force exerted by a driver of an automotive vehicle, especially in the case of heavy vehicles such as a truck, to actuate the clutch pedal.

[0002] As the load capacity of the trucks and consequently the power of the motors increases, it has become necessary to manufacture clutches having a greater pressure-plate load, which requires a greater effort on the part of the driver to actuate the clutch pedal.

[0003] The efforts of the prior art to solve this problem proved to be complex, expensive and, moreover, insufficient. An example of an attempt by the prior art to solve the problem is that described in U.S. Pat. No. 5,038,907, where a spring is used to exert force upon the clutch pedal so as to aid actuation. This system, however, is of complex construction and high cost, and does not provide good modulation in actuating the clutch.

[0004] Therefore, it is an objective of the invention to provide a system to reduce the force to actuate the clutch pedal in automobiles, particularly heavy vehicles such as trucks.

[0005] Another objective of the invention is to provide an inexpensive system that is not complex.

[0006] These objectives are achieved by this invention that provides a system reducing the force to actuate the clutch pedal in automobiles, which comprises an actuating arm provided at one end with a pedal and, at the other, with a pivot pin for the clutch master cylinder rod, the mentioned actuating arm being pivoted about a point located between its two ends, so that a force applied to the pedal causes the other end of the actuating arm to push the rod of the clutch master cylinder. The master cylinder itself is pivotable around at least one pin fixed on a vehicle body support, and the actuating arm, upon actuating the pedal, describes a rotational path for the pivot pin around the pivot point between the 2 ends of the actuating arm, so that the component of the lever arm that constitutes the moment applied to the pin between the ends of the actuating arm gradually decreases, thus reducing the moment applied to the pivot pin and the effort of the driver to actuate the clutch.

[0007] This invention is described below with reference to two embodiments, illustrated in the drawings, in which:

[0008]FIG. 1 is a schematic plane side view showing a clutch pedal typical of the prior art and in rest position, that is, without the pedal being pressed;

[0009]FIG. 2 is a view similar to FIG. 1, showing the pedal of the prior art in pressed or actuated position;

[0010]FIG. 3 is a schematic plane side view of a clutch pedal in a first embodiment, incorporating the teachings of this invention, in rest position;

[0011]FIG. 4 is a view similar to FIG. 2 showing the pedal of the first embodiment in pressed or actuated position of the clutch;

[0012]FIG. 5 is a schematic plane side view of a clutch pedal of a second embodiment, incorporating the teachings of this present invention, in rest position; and

[0013]FIG. 6 is a view similar to FIG. 2, showing the pedal of the second embodiment in pressed or actuated position.

DESCRIPTION OF THE PRIOR ART

[0014] First, with reference to FIGS. 1 and 2 of the drawings that illustrate a conventional clutch pedal, one can see that the system is made up of an actuating arm 1 having, at one end, a pedal 2 to be actuated by the driver of the vehicle (not shown) and, at the other end, a pivot pin 3 coupled to the free end of the rod 4 of the clutch master cylinder 5. The actuating arm 1 is pivoted around a pivot pin 6, at a point located between the two ends.

[0015] When the pedal is pressed, assuming the position illustrated in FIG. 2, the actuating arm 1 pivots around the pivot pin 6, thus causing the pivot pin 3 situated at the other end of the arm 1 to push the rod 4 of the master cylinder 5, thereby actuating the clutch.

[0016] There is still a spring or the like actuating to maintain the pedal in its rest or non-pressed position. This spring has been omitted in this specification as well as in the drawings for the sake of a better view of the drawings and because it is not part of this invention.

[0017] In an environment of the prior art, the moment exerted by the driver to actuate the plunger 4 of the master cylinder 5 is constant from beginning to end of the movement and can be expressed by the equation I below.

Fi×Y=Fh×X,  I

[0018] wherein Fi is the force actuating on the arm 1; Fh is the force on the rod 4 of the plunger of the master cylinder 5; X is the distance between the longitudinal axes of the pins 3 and 6; and Y is the distance between the pedal 2 and the pivot pin 6 of the actuating arm.

[0019] This pedal-actuating force, taking an average of the trucks on the market these days, ranges from 18 kgf for light trucks, 22 kgf for medium trucks and 25 kgf for heavy trucks, when they are new. With use, that force may increase by up to about 30% (thirty percent) above the initial value, due to the wear of the friction material, wear of the joints and loss of lubrication.

DESCRIPTION OF THE INVENTION

[0020] The system illustrated in FIGS. 1 and 2 having been described, the preferred embodiments of the invention will now be described, illustrated in FIGS. 3-6, where the reference numbers designating parts common to the system in both the prior art and the present are maintained in order to facilitate understanding.

[0021] A first embodiment of the system of this invention can be seen in FIGS. 3 and 4. The system comprises, two pins 9 on the master cylinder 5 driven in the support 10, the pins 9 turning freely inside the housing of the master cylinder 5. The cylinder 5 being consequently pivotable around the pins 9.

[0022] In operation, when the pedal 2 is pressed by the driver, the actuating arm 1 pivots around the pivot pin 6, causing its other end, provided with the pivot pin 3, to push the rod 4 of the plunger of the clutch master cylinder 5 into the latter. Throughout this movement, the pivot pit 3 follows a rotational path A (FIG. 3) around the pivot pin 6 of the actuating arm. While following the rotational path, the pivot pin 3 is accommodated by the clutch master cylinder 5, so as to enable the rod 4 to penetrate further into the clutch master cylinder 5.

[0023] Along this rotational path A of the pivot pin 3, the lever arm X turns around the pivot pin 6 and subtends an angle θ, as shown in FIG. 3, between its initial position (before the clutch pedal 2 is pressed) and its position at any point whatever along the path (while pressing the pedal 2). As the lever arm turns along the path A, the angle e increases and the component of the lever arm X, which is perpendicular to the rod 4 of the master cylinder 5, gradually decreases. The component, together with the force Fh applied to the rod 4, gives rise to the moment applied to the pivot pin 6. Therefore, the gradual decrease of the component causes a gradual decrease in moment on the pivot pin 6 and, consequently, a decrease in the effort made by the driver upon actuating the clutch pedal. The above description can be clearly seen by means of the relationships indicated below.

[0024] As already seen above, equation I

Fi×Y=Fh×X  I

[0025] On the other hand, according to this embodiment, as explained above, the component of the lever arm X, which is perpendicular to the rod 4, decreases as the angle θ increases. Therefore, according to the trigonometry, the component is equal to the lever arm X multiplied by the cosine of θ. Then, from equation I it follows that:

Fi×Y=Fh×X×cos θ,  II,

[0026] causing the value of the final pedal-actuating force Ff to be given by equation III below:

Ff=Fh×X×(cos θ)Y  III,

[0027] where Ff depends upon θ. The reduction of the actuating effort is represented by the following equation IV:

Reduction of the effort=1−Ff/Fi  IV.

[0028] Finally, the lever arm X of this embodiment has been designed with reduced dimensions, compared with those of the state of the art system, so as to contribute to a decrease in the moment applied on the pin 6 as well.

[0029] This reduction of effort, achieved by the system in this invention, if applied to vehicles in operation today, is in the order of 30% (thirty percent).

[0030]FIGS. 5 and 6 illustrate a second embodiment of the system of the invention, wherein the system comprises, at the other end of the actuating arm 1, a connecting means to link the rod of the clutch master cylinder, consisting, in addition to the pivot pin 3 itself, an integral part of the other end of the actuating arm 1, a direction means that includes a pivot guide-bar 7, fixed at one of its ends to the vehicle body, and, at the opposite end, to the pivot pin 3 and a slot 8 provided in the actuating arm I and through which the pivot pin 3 extends. The slot 8 extends from the actuating arm I to a point close to the pivot pin 6 of the arm 1.

[0031] The clutch master cylinder utilized by the invention is pivotable around two pins 9 driven into the support 10. The pins 9 turn freely inside the housing of the master cylinder In operation, when the pedal 2 is pressed by the driver, the actuating arm 1 pivots around the pivot pin 6, causing its other end, provided with the pivot pin 3, to push the plunger rod of the clutch master cylinder 5 into the latter. This movement of the pivot pin 3, however, is guided under the action of the guide-bar 7 combined with the slot 8, so that the pin will move close to the pivot pin 6 of the actuating arm 1, in reality following the curved path B indicated in FIG. 5. This curved movement of the pivot pin 3 is accommodated by the pivoting of the clutch master cylinder 5, so that the rod 4, just as in the first embodiment, will penetrate further into the cylinder 5.

[0032] The progressive decrease in the distance between the pivot pin 3 and the pivot pin 6, in effect, reduces the lever arm to which the force Fh is applied on the plunger rod 4 of the master cylinder 5, thus reducing the value of the moment and, consequently, the effort made by the driver to actuate the clutch pedal, as can be clearly seen in the relationships indicated below:

[0033] As already seen above, from equation I

Fi×Y=Fh×X,  I

[0034] results in the following equation V

Fi=Fh×X/Y  V

[0035] On the other hand, according to the second embodiment explained above, the value of X decreases as the pedal 2 is pressed (making Xf<X), causing the value of the final pedal-driving force Ff to be given by the equation VI below:

Ff=Fh×Xf/Y  VI

[0036] wherein Ff is less than Fi. The reduction of the actuating effort is represented by the following equation VII:

Reduction=1−Ff/Fi  IV

[0037] The reduction of effort achieved by this embodiment of the system is similar to that achieved by the first embodiment.

[0038] It should be rememebered that only two preferred embodiments of the invention have been described above, various others being possible, without departing from the inventive concept to be protected, which is only limited by the accompanying claims. 

1. A system for reducing the force to actuate the clutch pedal in automobiles, wherein the clutch-actuating pedal (2) is fixed to one end of an actuating arm (1), which has, at its other end, a pivot pin (3) of the rod (4) of the clutch master cylinder (5), the actuating arm (1) being further pivoted around a pivot pin (6) located between its ends and fixed to the vehicle body (not shown), so that a force applied on to the pedal (2) causes the pivot pin (3), provided at the other end of the actuating arm (1), to actuate, pressing the plunger rod (4) of the clutch master cylinder (5); the system being characterized in that the master cylinder (5) itself is pivotable around at least one pin fixed to the support (10) on the vehicle body (not shown).
 2. A system according to claim 1, characterized in that the master cylinder (5) is pivotable around two pins (9) fixed to the support (10).
 3. A system according to claim 2, characterized in that the two pins (9) are driven into the support (10) and turn freely inside the body of the master cylinder (5).
 4. A system for reducing the force to actuate the clutch pedal in automobiles, wherein the clutch-actuating pedal (2) is fixed to one end of an actuating arm (1), which has, at its other end, a connecting means for linking to the rod (4) of the clutch master cylinder (5), the connecting means comprising a pivot pin (3), which is an integral part of the free end of the rod (4), the actuating arm (1) being further pivoted around a pivot pin (6) located between its ends and fixed to the vehicle body (not shown), so that the force applied to the pedal (2) causes the pivot pin (3), provided at the other end of the actuating arm (1), to actuate, pressing the rod (4) of the plunger of the clutch master cylinder (5); the system being characterized by the fact that the connecting means for linking to the rod (4) of the clutch master cylinder (5) further comprises a direction means (7,8) cooperating with the pivot pin (3) and that define a path (A) for the pivot pin (3), upon actuating the pedal (2), the path (A) extending from the other end of the actuating arm (1) to a point closer to the pivot pin (6) of the actuating arm (1); and the master cylinder (5) itself is pivotable around a pin (9) fixed to its side wall and to the vehicle body (not shown).
 5. A system according to claim 4, characterized by the fact that the direction means consists of a guide-bar (7), pivotally fixed at one of its ends to the vehicle body (not shown) and, at the opposite end, to the pivot pin (3); and a slot (8) provided in the actuating arm (1) and through which the pivot pin (3) extends, the slot (8) extending from the other end of the actuating arm (1) to a point closer to the pivot pin (6) of the arm (1). 